JPS6224374B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a magnesia cement molded body with improved heat resistance. The hardened magnesia cement is dense and hard, and its mechanical properties, especially the bending strength, are superior to those of the hardened Portland cement, and by further reinforcing it with fibers, it can exhibit mechanical properties equivalent to those of synthetic resins. Furthermore, the nonflammability of magnesia cement compensates for the weaknesses of conventional synthetic resins, making it highly useful for disaster prevention. The strength development of hardened magnesia cement is similar to that of hardened materials such as Portland cement and alumina cement.
3MgO・MgCl ₂・12H ₂ O and 5MgO・MgCl ₂・13H ₂ O
It is known that it is caused by hydrated double salt minerals such as
The mechanical properties of the cured product differ depending on the type and form of the hydrous double salt mineral produced, and the thermal stability also varies. For this reason, the hardened magnesia cement has the disadvantage that if it is kept under high temperature dry conditions for a long period of time, cracks will occur and the mechanical properties will be significantly reduced. Conventionally, as a method to improve such shortcomings,
A method has been proposed in which reinforcing fibers, such as glass fibers, are added to magnesia cement. Although this method is effective in preventing the occurrence of large cracks, it is effective in preventing minute cracks occurring in the surface layer of the hardened magnesia cement. cannot be prevented. Therefore, although it has the important advantage of being nonflammable, it has the disadvantage that its thermal stability, that is, heat resistance, is inferior to that of conventional synthetic resins. In view of the above-mentioned current situation, the present invention provides a method for producing a magnesia cement molded body that is nonflammable, does not cause cracks, has good mechanical properties, and has excellent thermal stability, that is, heat resistance. The purpose of this research is to provide a molded article of magnesia cement, which is characterized in that a molded article of a magnesia cement curable composition is carbonated in a carbon dioxide gas-containing atmosphere under heating and pressure. It depends on the manufacturing method. The magnesia cement curable composition in the present invention is a composition in which water is added to magnesia cement and mixed.
Refers to an uncured composition that is cured by heating or over time. The composition is then shaped into a plate, cylinder, or other desired shape. As the magnesia cement, conventionally known magnesia cement compositions containing activated magnesia and magnesium chloride and/or magnesium sulfate as main components can be used, but in order to improve water resistance, it is possible to use water-based cement compounds such as tribasic magnesium phosphate. Preferably, it contains an insoluble phosphate. Further, the magnesia cement hardening composition may contain fibers such as glass fibers, mineral slag fibers, rock fibers, metal fibers, natural fibers, synthetic fibers, or mat-like materials or woven materials made of such fibers for reinforcement. Alternatively, various aggregates, fillers, etc. may be added. The carbonation treatment of the excipient of the magnesia cement curable composition in the present invention can be carried out either during heat curing or curing of the excipient. Preferably, this is carried out during heat curing of the excipient. The shaped product of the magnesia cement curable composition in the present invention is one in which the magnesia cement curable composition is simply shaped into a specific shape, and it is precured at room temperature or by heating. Further, the carbonation treatment of the excipient of the magnesia cement curable composition in the present invention is carried out in a carbon dioxide gas-containing atmosphere under heating and pressure, and even if the temperature of the atmosphere is too low, the effect of the present invention will not be achieved. In the present invention, it is preferable to carry out the carbonation treatment in the range of 40°C to 180°C, since it is difficult to predict and if the temperature is too high, the mechanical properties of the cured product tend to deteriorate. Further, the pressure of the carbon dioxide gas-containing atmosphere is not particularly limited, but in order to expect the effects of the present invention, it is preferably equal to or higher than the saturated water vapor pressure of the heating temperature. The carbon dioxide concentration in the present invention is interrelated with the shape and thickness of the excipient, the temperature and pressure of the atmosphere, etc., and is not particularly limited. preferable. In addition, in the carbonation treatment of the present invention, if the carbon dioxide gas-containing atmosphere at the time of the treatment is dry, it is difficult to expect the effects of the present invention. It is preferable to carry out the process in a state where an appropriate amount of moisture is present in the shaped object, and in this case, it is desirable that the relative humidity in the carbon dioxide gas-containing atmosphere be at least 30% or higher. Further, the magnesia cement curable composition of the present invention can be cured by either a room temperature curing method or a heat curing method, and may also be heat cured in an atmosphere containing carbon dioxide gas. The method for producing the magnesia cement molded body of the present invention is as described above, and in particular, the molded body of the magnesia cement curable composition is carbonated in a carbon dioxide gas-containing atmosphere under heat and pressure. As a result, the reactivity between the excipient and carbon dioxide gas is increased, that is, carbonation is promoted, and not only the surface layer but also the inner layer of the excipient is carbonated in a short processing time, resulting in a magnesia cement molded body. Excellent heat resistance can be imparted, and according to the method of the present invention, even magnesia cement molded bodies under long-term aging can be carbonated without generating cracks, thereby imparting heat resistance. This makes it possible to expand the scope of application of the molded product to applications requiring heat resistance, such as industrial water supply and drainage pipes and piping materials for intake and exhaust. The present invention will be explained below based on examples. Example 1 A magnesia cement composition slurry prepared by mixing 100 parts by weight of activated magnesia, 40 parts by weight of magnesium chloride (anhydrous), 120 parts by weight of water, and 5 parts by weight of tribasic magnesium phosphate was poured into a 20 cm x 20 cm square mold. Molding and at the same time glass chopped strand mat
After being impregnated with magnesia cement in an amount equivalent to 8.5% by weight, the material was cured by heating in an oven at an ambient temperature of 80° C. for 1 hour to obtain a plate-shaped cured product with a thickness of 10 m/m. After demolding, the cured product is used in an autoclave.
Carbonation treatment was carried out for 20 hours in a 30% concentration carbon dioxide atmosphere (relative humidity 65%) at 65℃ and 2Kg/ ^cm2 pressure, and after curing in an atmospheric pressure atmosphere for another 21 days, the cured product was heated to ambient temperature. was kept in an oven at 120°C for 15 days to conduct a heat resistance test. The bending strength of the cured product thus obtained was measured in accordance with JISA1408 "Bending test method for architectural boards," and as shown in the column of Example 1 in Table 1, the bending strength was 620 kg/
cm ² , which was almost the same as the bending strength of the cured product before the heat resistance evaluation (630 Kg/cm ² ), indicating excellent heat resistance. Example 2 Glass chopped strand pine was added to the same magnesia cement composition slurry as in Example 1.
After being impregnated with an amount equivalent to 8.0% by weight and laminated, it was cured by heating in an autoclave at 60°C for 3 hours in a 30% carbon dioxide atmosphere (relative humidity 85%) under a pressure of ⁵ kg/cm 2 to a thickness of 3 m/cm2. A plate-shaped cured body of m was obtained. After demolding, the cured product was cured in the air for 21 days, and then held in an oven at an ambient temperature of 100° C. for 15 days to conduct a heat resistance test. The bending strength of the cured product thus obtained was measured in the same manner as in Example 1, and as shown in the column of Example 2 in Table 1, the bending strength was 585 Kg/cm ² , which was the same as before the heat resistance evaluation. The bending strength was almost the same as that of the cured product (590 Kg/cm ² ), and the heat resistance was excellent. Example 3 100 parts by weight of activated magnesia, 35 parts by weight of magnesium chloride (anhydrous) and 110 parts by weight of water were mixed, and a glass chopped strand with a length of 12 m/m was further added.
An amount equivalent to 3.0% by weight was added, poured into a 20 cm x 20 cm square mold, and cured at room temperature for one day to obtain a plate-shaped cured product with a thickness of 10 m/m. After demolding, the cured product was cured in the air for 21 days, and then heated in an autoclave at 85℃ and 5Kg/ ^cm2 pressure in a 30% carbon dioxide atmosphere (relative humidity 65%) for 48 hours. carbonated,
Furthermore, the cured product was kept under the same atmospheric conditions as in Example 2 for 15 days to conduct a heat resistance test. The bending strength of the thus obtained cured product was measured in the same manner as in Example 1. As shown in the column of Example 3 in Table 1, the bending strength was 310 Kg/cm ² , which was the same as before the heat resistance evaluation. The bending strength was almost the same as that of the cured product (335 kg/cm ² ), and the heat resistance was excellent. Comparative Example 1 Glass chopped strand pine was added to the same magnesia cement composition slurry as in Example 1.
After impregnation and lamination in an amount equivalent to 8.5% by weight, the ambient temperature
Heat cured in an oven at 80℃ for 1 hour to a thickness of 10
A plate-shaped cured body of m/m was obtained. The same cured product after demolding
After curing in the air for 21 days, the cured product was kept in an oven at an ambient temperature of 120° C. for 15 days to conduct a heat resistance test. The bending strength of the thus obtained cured product was measured in the same manner as in Example 1. As shown in the column of Comparative Example 1 in Table 1, the bending strength was 255 Kg/cm ² , which was the same as before the heat resistance evaluation. The bending strength was significantly lower than that of the cured product (650 Kg/cm ² ), and the heat resistance was poor. Example 4 A paper core with a diameter of 150 m/m was used as the core material of the pipe, a release paper was wrapped around the surface of the paper core, and 8.5 weight of glass roving fibers were added to the same magnesia cement composition slurry as in Example 1 on top of the paper core. % impregnated, and the outer surface was covered with release paper, and then heated and cured in an oven at an ambient temperature of 60°C for 1 hour to form a cured pipe with a wall thickness of 12 m/m and a diameter of 150 m/m. Obtained. After removing the core material and release paper, the cured product was heated at 70℃ using an autoclave.
4Kg/ ^cm2 in a pressurized 30% carbon dioxide atmosphere.
After carbonation treatment for a period of time and further curing in the air for 21 days, the cured product was kept in an oven at an ambient temperature of 120° C. for 15 days to conduct a heat resistance test. As a result of measuring the crushing strength of the cured product thus obtained, as shown in the column of Example 4 in Table 2, the crushing strength was 850Kg/ ^cm2 , and the crushing strength of the cured product before heat resistance evaluation was 870Kg/cm2. /cm ² ) and had excellent heat resistance.

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Claims (1)

[Scope of Claims] 1. A method for producing a magnesia cement molded article, which comprises carbonating a molded article of a magnesia cement curable composition in a carbon dioxide gas-containing atmosphere under heating and pressure. 2 The temperature of the atmosphere containing carbon dioxide is 40℃ to 180℃
A method for producing a magnesia cement molded body according to claim 1. 3. The method for producing a magnesia cement molded body according to claim 1 or 2, wherein the pressure of the carbon dioxide gas-containing atmosphere is equal to or higher than the saturated water vapor pressure at the heating temperature. 4. The method for producing a magnesia cement molded body according to claim 1, 2 or 3, wherein the carbon dioxide concentration is 0.1% or more.